GlobalWafers Co (環球晶圓), the world’s third-largest silicon wafer supplier, yesterday said it plans to issue unsecured convertible bonds of up to US$500 million in a private placement, with US memory chipmaker Micron Technology Inc as the sole subscriber.Hsinchu City-based GlobalWafers said in a state. Add TT as Preferred Source GlobalWafers Co (環球晶圓), the world’s third-largest silicon wafer supplier, yesterday said it plans to issue unsecured convertible bonds of up to US$500 million.